This invention relates to the preparation of magnesium compound-impregnated catalyst compositions comprising a crystalline gallosilicate molecular sieve incorporated into an inorganic matrix and to processes for selectively ethylating toluene accomplished by contacting toluene and an ethylating agent under hydrocarbon conversion conditions with said compositions. More particularly, the invention relates to the preparation of magnesium compound-impregnated catalyst compositions comprising high surface area, essentially free of aluminum, crystalline gallosilicate-based molecular sieves incorporated into an inorganic matrix, and toluene conversion processes using such catalyst compositions comprising contacting ethylene and toluene under conversion conditions to form an ethyltoluene product in which the paraselectivity is nearly one hundred percent at excellent percent conversions.
In the commercial preparation of p-ethyltoluene for use to make p-methylstyrene, it is economically important that the method used to make the ethyltoluene makes a highly isomerically pure material. Separation of similar-in-property isomers prior to dehydrogenation of the ethyltoluene to the styrene compound is thus avoided. Paraselective catalysts useful for the gas-phase ethylation of toluene which can produce a product with greater than 95% isomeric purity are thus a highly desirable commercial objective.
A number of recent patents have claimed the formation of gallosilicate-type molecular sieves or gallium compound impregnated/exchanged sieves of various structures which are said to be useful for a variety of catalytic purposes. For example, U.S. Pat. Nos. 4,372,930 and 4,450,312 teach gallosilicate molecular sieves of Structure Types Nu-3 and Nu-5 which are claimed to be useful for the selective alkylation of alkanes and the isomerization of xylenes, respectively. U.S. Pat. No. 4,444,652 teaches the formation of gallium compound impregnated/exchanged sieves for upgrading low grade gasolines. In U.S. Pat. No. 4,377,502, the alkylation of toluene using a variety of crystalline aluminosilicate sieves is set forth. The patent teaches that the aluminum may be substituted by gallium. And in U.S. Pat. No. 4,276,437 ZSM-5 molecular sieve catalyst compositions impregnated with gallium and phosphorus compounds are taught for the selective paraethylation of toluene.
In Japanese Patent Application Kokai 60-19726 a gallosilicate of the ZSM-5 structure impregnated with a phosphorus oxide is used to improve alkylation paraselectivity when the sieve is used for the ethylation of toluene.
In U.S. Pat. Nos. 4,504,690, 4,128,592, and 4,086,287 the modifying of a ZSM-5 aluminosilicate zeolite catalyst with P, Mg, or P/Mg oxides to obtain high proportions of the 1,4-dialkyl isomer during alkylation is taught. Phosphorus or Mg-modified ZSM-5 zeolite catalysts for the disproportionation of toluene are described in J. Appl. Polym. Sci. 36, 209 (1981). Disproportionation of toluene to produce benzene over P, Mg-modified crystalline aluminosilicate zeolite catalysts is described in U.S. Pat. No. 4,137,195. Alkylation or disproportionation of certain monosubstituted benzene compounds to achieve nearly 100% selectivity to paradisubstituted derivatives over magnesium compound-modified ZSM-5 aluminosilicate zeolite catalysts is reported in J. Am. Chem. Soc. 101, 6783 (1979). Use of Mg alone or in combination with P to modify a ZSM-5 aluminosilicate zeolite catalyst is described in U.S. Pat. No. 4,049,573 and the modified catalyst is used for converting alcohols and ethers to hydrocarbons. Again, Mg is used to modify ZSM-5 zeolite catalysts in U.S. Pat. No. 4,002,698, which can be used for selective production of p-xylene from charge stocks of toluene and a C.sub.3 -C.sub.10 olefin.